1. Field of the Invention
This invention relates to a soft contact lens and a process for producing the same, and, more particularly, to a non-hydrous soft contact lens having high oxygen permeability and good mechanical strength, etc., and a process for producing the same.
2. Description of Prior Art
As soft contact lenses, there are known hydrous soft contact lenses made of hydrous polymers such as poly-2-hydroxyethyl methacrylate, and non-hydrous soft contact lenses made of silicone polymers or the like. The hydrous soft contact lenses, in general, have such an insufficient oxygen permeability that they are apt to damage the metabolism of corneal tissues, or require frequent sterilization by boiling to prevent the propagation of bacteria and the like, thereby being cumbersome. In contrast with this, the non-hydrous soft contact lenses made of silicone polymers have good oxygen permeability, but are accompanied with the problem that they tend to be contaminated by lachrymal components to cause a blur of contact lens after continuous wear for a long period of time, which blue can not be removed by cleaners.
Also, it is desirable for soft contact lenses to have good affinity for eyes without any feeling of foreign matters. Japanese Patent Publication (KOKOKU) No. 33887/1984 discloses a process for producing a non-hydrous soft contact lens having good affinity for an eye, comprising subjecting a lens substrate mainly comprising a polyacrylate or polymethacrylate and having the shape of a contact lens to esterification treatment and/or transesterification treatment. This contact lens, however, is disadvantageous in that it has insufficient oxygen permeability and therefore can not be worn for a long time, and also has a low mechanical strength.
Now, it has been sought after to develop a soft contact lens that may require no sterilization by boiling and causes no metabolism disorder in the corneal textures even after wearing for a long time, in other words, a soft contact lens of non-hydrous type, having resistance to the stain by lachrymal components and having good oxygen permeability.
As such a contact lens, for example, U.S. Pat. No. 3,808,179 discloses a contact lens comprising a copolymer of a fluoroalkylester of acrylic acid or methacrylic acid with an alkyl ester of acrylic acid or methacrylic acid. Japanese Patent Publication (KOKOKU) No. 46614/1976 also discloses a soft contact lens comprising a copolymer of methyl methacrylate with a fluoroalkyl methacrylate.
The soft contact lens described in the U.S. Pat. No. 3,808,179, however, involves problems that it has a low mechanical strength and tends to be broken when handled, and the soft contact lens described in Japanese Patent Publication (KOKOKU) No. 46614/1976 also involves the problem that it has a low oxygen permeability because of the employment of methyl methacrylate.
The present inventors disclosed in U.S. Pat. No. 4,737,556 a non-hydrous soft contact lens capable of solving the problems mentioned above, which comprises a copolymer comprising, as monomer units, 49.9 to 95 mole % of an acrylate represented by Formula (I) shown below, 0 to 10 mole % of at least one selected from the group consisting of acrylic acid, an acrylic acid alkyl ester or acrylic acid fluoroalkyl ester whose alkyl group or fluoroalkyl group has 1 to 3 carbon atoms, 4.9 to 50 mole % of a methacrylate represented by Formula (II) shown below, and 0.1 to 10 mole % of a crosslinking monomer, and processes for preparing it. ##STR3## wherein R.sup.1 is at least one selected from the group consisting of a straight chain fluoroalkyl group represented by the formula: --(CH.sub.2).sub.l --C.sub.m F.sub.n H.sub.p, where l is an integer of 1 or 2, m is an integer of 3 to 8, n is an integer of 6 or more, p is an integer of 0 or more, and m, n and p satisfy the equation: n+p=2m+1; and a straight chain alkyl group represented by the formula: --C.sub.q H.sub.2q+1, where q is an integer of 4 to 10. ##STR4## wherein R.sup.2 is a straight chain fluoroalkyl group represented by the formula: --C.sub.x F.sub.y H.sub.z, where x is an integer of 0 or more, and x, y and z satisfy the equation: y+z=2x+1.